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Ralph Tiedemann - One of the best experts on this subject based on the ideXlab platform.
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intragenus f1 hybrids of african weakly electric fish Mormyridae campylomormyrus tamandua c compressirostris are fertile
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2020Co-Authors: Yevheniia Korniienko, Ralph Tiedemann, Linh Nguyen, Marianne Vater, Stephanie Baumgartner, Frank KirschbaumAbstract:Hybridization is widespread in fish and constitutes an important mechanism in fish speciation. There is, however, little knowledge about hybridization in mormyrids. F1-interspecies hybrids between Campylomormyrus tamandua ♂ × C. compressirostris ♀ were investigated concerning: (1) fertility; (2) survival of F2-fish and (3) new gene combinations in the F2-generation concerning the structure of the electric organ and features of the electric organ discharge. These F1-hybrids achieved sexual maturity at about 12–13.5 cm total length. A breeding group comprising six males and 13 females spawned 28 times naturally proving these F1-fish to be fertile. On average 228 eggs were spawned, the average fertilization rate was 47.8%. Eggs started to hatch 70–72 h after fertilization, average hatching rate was 95.6%. Average mortality rate during embryonic development amounted to 2.3%. Average malformation rate during the free embryonic stage was 27.7%. Exogenous feeding started on day 11. In total, we raised 353 normally developed larvae all of which died consecutively, the oldest specimen reaching an age of 5 months. During survival, the activities of the larval and adult electric organs were recorded and the structure of the adult electric organ was investigated histologically.
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Ontogeny of electric organ and electric organ discharge in Campylomormyrus rhynchophorus (Teleostei: Mormyridae)
Journal of Comparative Physiology A, 2020Co-Authors: Linh Nguyen, Victor Mamonekene, Ralph Tiedemann, Peter Bartsch, Marianne Vater, Frank KirschbaumAbstract:The aim of this study was a longitudinal description of the ontogeny of the adult electric organ of Campylomormyrus rhynchophorus which produces as adult an electric organ discharge of very long duration (ca. 25 ms). We could indeed show (for the first time in a mormyrid fish) that the electric organ discharge which is first produced early during ontogeny in 33-mm-long juveniles is much shorter in duration and has a different shape than the electric organ discharge in 15-cm-long adults. The change from this juvenile electric organ discharges into the adult electric organ discharge takes at least a year. The increase in electric organ discharge duration could be causally linked to the development of surface evaginations, papillae, at the rostral face of the electrocyte which are recognizable for the first time in 65-mm-long juveniles and are most prominent at the periphery of the electrocyte.
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Reproduction and development in some species of the weakly electric genus Campylomormyrus (Mormyridae, Teleostei)
Environmental Biology of Fishes, 2017Co-Authors: Linh Nguyen, Christiane Paul, Victor Mamonekene, Ralph Tiedemann, Peter Bartsch, Frank KirschbaumAbstract:Reproduction in captivity of four species of the mormyrid genus Campylomormyrus was investigated. Cyclical reproduction was provoked by changing water conductivity (C) alone: decreasing C led to gonadal recrudescence, an increase induced gonad regression. Data on the reproduction and development of three species are presented. All three species are indeterminate fractional spawners. Spawning intervals ranged from 6 to 66 days in C. rhynchophorus , 10–75 days in C. tshokwe , and 18 days in C. compressirostris (calculated values). Fecundities (eggs per fractional spawning) ranged from 70 to 1570 eggs in C. rhynchophorus , 100–1192 in C. tshokwe , and 38–246 in C. compressirostris . Spawnings/ovipositions occurred during the second half of the night; no parental care was observed; no special spawning substrates were necessary. C. compressirostris successfully spawned in breeding groups, C. rhynchophorus as pair. Agonistic behavior in the C. tshokwe pair forced us to divide the breeding tank; therefore, only ovipositions occurred. However, injection of an artificial GnRH hormone allowed us to obtain ripe eggs and sperm and to perform successful artificial reproduction. All three species produce yolky, slightly sticky eggs. Egg diameter ranges from 2.3–3.0 mm. Hatching occurred on day 3, feeding started on day 11. Transition from larval to juvenile stage occurred at around 20 mm total length (TL). At this size C. rhynchophorus developed a higher body than the two other species and differences between the species in the melanin pigmentation of the unpaired fins occurred. Between 32 and 35 mm TL the upper and lower jaws started to elongate.
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Evidence for Non-neutral Evolution in a Sodium Channel Gene in African Weakly Electric Fish (Campylomormyrus, Mormyridae)
Journal of Molecular Evolution, 2016Co-Authors: Christiane Paul, Victor Mamonekene, Frank Kirschbaum, Ralph TiedemannAbstract:Voltage-gated sodium channels, Nav1, play a crucial role in the generation and propagation of action potentials and substantially contribute to the shape of their rising phase. The electric organ discharge (EOD) of African weakly electric fish (Mormyroidea) is the sum of action potentials fired from all electrocytes of the electric organ at the same time and hence voltage-gated sodium channels are one factor—together with the electrocyte’s morphology and innervation pattern—that determines the properties of these EODs. Due to the fish-specific genome duplication, teleost fish possess eight copies of sodium channel genes (SCN), which encode for Nav1 channels. In mormyroids, SCN4aa is solely expressed in the electrocytes of the adult electric organ. In this study, we compared entire SCN4aa sequences of six species of the genus Campylomormyrus and identified nonsynonymous substitutions among them. SCN4aa in Campylomormyrus exhibits a much higher evolutionary rate compared to its paralog SCN4ab, whose expression is not restricted to the electric organ. We also found evidence for strong positive selection on the SCN4aa gene within Mormyridae and along the lineage ancestral to the Mormyridae. We have identified sites at which all nonelectric teleosts are monomorphic in their amino acid, but mormyrids have different amino acids. Our findings confirm the crucial role of SCN4aa in EOD evolution among mormyrid weakly electric fish. The inferred positive selection within Mormyridae makes this gene a prime candidate for further investigation of the divergent evolution of pulse-type EODs among closely related species.
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species delimitation and phylogenetic relationships in a genus of african weakly electric fishes osteoglossiformes Mormyridae campylomormyrus
Molecular Phylogenetics and Evolution, 2016Co-Authors: Philine G D Feulner, Christiane Paul, Victor Mamonekene, Frank Kirschbaum, Francesco Lamanna, Anja Ernst, Ralph TiedemannAbstract:African weakly-electric fishes (Mormyridae) are able to communicate through species-specific electric signals; this feature might have favoured the evolutionary radiation observed in this family (over 200 species) by acting as an effective pre-zygotic isolation mechanism. In the present study we used mitochondrial (cytb) and nuclear (rps7, scn4aa) markers in order to reconstruct a species-phylogeny and identify species boundaries for the genus Campylomormyrus, by applying inference methods based on the multispecies coalescent model. Additionally, we employed 16 microsatellite markers, landmark-based morphometric measurements, and electro-physiological analyses as independent lines of evidence to the results obtained from the sequence data. The results show that groups that are morphologically different are also significantly divergent at the genetic level, whereas morphologically similar groups, displaying dissimilar electric signals, do not show enough genetic diversity to be considered separate species. Furthermore, the data confirm the presence of a yet undescribed species within the genus Campylomormyrus.
Frank Kirschbaum - One of the best experts on this subject based on the ideXlab platform.
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intragenus f1 hybrids of african weakly electric fish Mormyridae campylomormyrus tamandua c compressirostris are fertile
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2020Co-Authors: Yevheniia Korniienko, Ralph Tiedemann, Linh Nguyen, Marianne Vater, Stephanie Baumgartner, Frank KirschbaumAbstract:Hybridization is widespread in fish and constitutes an important mechanism in fish speciation. There is, however, little knowledge about hybridization in mormyrids. F1-interspecies hybrids between Campylomormyrus tamandua ♂ × C. compressirostris ♀ were investigated concerning: (1) fertility; (2) survival of F2-fish and (3) new gene combinations in the F2-generation concerning the structure of the electric organ and features of the electric organ discharge. These F1-hybrids achieved sexual maturity at about 12–13.5 cm total length. A breeding group comprising six males and 13 females spawned 28 times naturally proving these F1-fish to be fertile. On average 228 eggs were spawned, the average fertilization rate was 47.8%. Eggs started to hatch 70–72 h after fertilization, average hatching rate was 95.6%. Average mortality rate during embryonic development amounted to 2.3%. Average malformation rate during the free embryonic stage was 27.7%. Exogenous feeding started on day 11. In total, we raised 353 normally developed larvae all of which died consecutively, the oldest specimen reaching an age of 5 months. During survival, the activities of the larval and adult electric organs were recorded and the structure of the adult electric organ was investigated histologically.
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Ontogeny of electric organ and electric organ discharge in Campylomormyrus rhynchophorus (Teleostei: Mormyridae)
Journal of Comparative Physiology A, 2020Co-Authors: Linh Nguyen, Victor Mamonekene, Ralph Tiedemann, Peter Bartsch, Marianne Vater, Frank KirschbaumAbstract:The aim of this study was a longitudinal description of the ontogeny of the adult electric organ of Campylomormyrus rhynchophorus which produces as adult an electric organ discharge of very long duration (ca. 25 ms). We could indeed show (for the first time in a mormyrid fish) that the electric organ discharge which is first produced early during ontogeny in 33-mm-long juveniles is much shorter in duration and has a different shape than the electric organ discharge in 15-cm-long adults. The change from this juvenile electric organ discharges into the adult electric organ discharge takes at least a year. The increase in electric organ discharge duration could be causally linked to the development of surface evaginations, papillae, at the rostral face of the electrocyte which are recognizable for the first time in 65-mm-long juveniles and are most prominent at the periphery of the electrocyte.
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Reproduction and development in some species of the weakly electric genus Campylomormyrus (Mormyridae, Teleostei)
Environmental Biology of Fishes, 2017Co-Authors: Linh Nguyen, Christiane Paul, Victor Mamonekene, Ralph Tiedemann, Peter Bartsch, Frank KirschbaumAbstract:Reproduction in captivity of four species of the mormyrid genus Campylomormyrus was investigated. Cyclical reproduction was provoked by changing water conductivity (C) alone: decreasing C led to gonadal recrudescence, an increase induced gonad regression. Data on the reproduction and development of three species are presented. All three species are indeterminate fractional spawners. Spawning intervals ranged from 6 to 66 days in C. rhynchophorus , 10–75 days in C. tshokwe , and 18 days in C. compressirostris (calculated values). Fecundities (eggs per fractional spawning) ranged from 70 to 1570 eggs in C. rhynchophorus , 100–1192 in C. tshokwe , and 38–246 in C. compressirostris . Spawnings/ovipositions occurred during the second half of the night; no parental care was observed; no special spawning substrates were necessary. C. compressirostris successfully spawned in breeding groups, C. rhynchophorus as pair. Agonistic behavior in the C. tshokwe pair forced us to divide the breeding tank; therefore, only ovipositions occurred. However, injection of an artificial GnRH hormone allowed us to obtain ripe eggs and sperm and to perform successful artificial reproduction. All three species produce yolky, slightly sticky eggs. Egg diameter ranges from 2.3–3.0 mm. Hatching occurred on day 3, feeding started on day 11. Transition from larval to juvenile stage occurred at around 20 mm total length (TL). At this size C. rhynchophorus developed a higher body than the two other species and differences between the species in the melanin pigmentation of the unpaired fins occurred. Between 32 and 35 mm TL the upper and lower jaws started to elongate.
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Evidence for Non-neutral Evolution in a Sodium Channel Gene in African Weakly Electric Fish (Campylomormyrus, Mormyridae)
Journal of Molecular Evolution, 2016Co-Authors: Christiane Paul, Victor Mamonekene, Frank Kirschbaum, Ralph TiedemannAbstract:Voltage-gated sodium channels, Nav1, play a crucial role in the generation and propagation of action potentials and substantially contribute to the shape of their rising phase. The electric organ discharge (EOD) of African weakly electric fish (Mormyroidea) is the sum of action potentials fired from all electrocytes of the electric organ at the same time and hence voltage-gated sodium channels are one factor—together with the electrocyte’s morphology and innervation pattern—that determines the properties of these EODs. Due to the fish-specific genome duplication, teleost fish possess eight copies of sodium channel genes (SCN), which encode for Nav1 channels. In mormyroids, SCN4aa is solely expressed in the electrocytes of the adult electric organ. In this study, we compared entire SCN4aa sequences of six species of the genus Campylomormyrus and identified nonsynonymous substitutions among them. SCN4aa in Campylomormyrus exhibits a much higher evolutionary rate compared to its paralog SCN4ab, whose expression is not restricted to the electric organ. We also found evidence for strong positive selection on the SCN4aa gene within Mormyridae and along the lineage ancestral to the Mormyridae. We have identified sites at which all nonelectric teleosts are monomorphic in their amino acid, but mormyrids have different amino acids. Our findings confirm the crucial role of SCN4aa in EOD evolution among mormyrid weakly electric fish. The inferred positive selection within Mormyridae makes this gene a prime candidate for further investigation of the divergent evolution of pulse-type EODs among closely related species.
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species delimitation and phylogenetic relationships in a genus of african weakly electric fishes osteoglossiformes Mormyridae campylomormyrus
Molecular Phylogenetics and Evolution, 2016Co-Authors: Philine G D Feulner, Christiane Paul, Victor Mamonekene, Frank Kirschbaum, Francesco Lamanna, Anja Ernst, Ralph TiedemannAbstract:African weakly-electric fishes (Mormyridae) are able to communicate through species-specific electric signals; this feature might have favoured the evolutionary radiation observed in this family (over 200 species) by acting as an effective pre-zygotic isolation mechanism. In the present study we used mitochondrial (cytb) and nuclear (rps7, scn4aa) markers in order to reconstruct a species-phylogeny and identify species boundaries for the genus Campylomormyrus, by applying inference methods based on the multispecies coalescent model. Additionally, we employed 16 microsatellite markers, landmark-based morphometric measurements, and electro-physiological analyses as independent lines of evidence to the results obtained from the sequence data. The results show that groups that are morphologically different are also significantly divergent at the genetic level, whereas morphologically similar groups, displaying dissimilar electric signals, do not show enough genetic diversity to be considered separate species. Furthermore, the data confirm the presence of a yet undescribed species within the genus Campylomormyrus.
Philine G D Feulner - One of the best experts on this subject based on the ideXlab platform.
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species delimitation and phylogenetic relationships in a genus of african weakly electric fishes osteoglossiformes Mormyridae campylomormyrus
Molecular Phylogenetics and Evolution, 2016Co-Authors: Philine G D Feulner, Christiane Paul, Victor Mamonekene, Frank Kirschbaum, Francesco Lamanna, Anja Ernst, Ralph TiedemannAbstract:African weakly-electric fishes (Mormyridae) are able to communicate through species-specific electric signals; this feature might have favoured the evolutionary radiation observed in this family (over 200 species) by acting as an effective pre-zygotic isolation mechanism. In the present study we used mitochondrial (cytb) and nuclear (rps7, scn4aa) markers in order to reconstruct a species-phylogeny and identify species boundaries for the genus Campylomormyrus, by applying inference methods based on the multispecies coalescent model. Additionally, we employed 16 microsatellite markers, landmark-based morphometric measurements, and electro-physiological analyses as independent lines of evidence to the results obtained from the sequence data. The results show that groups that are morphologically different are also significantly divergent at the genetic level, whereas morphologically similar groups, displaying dissimilar electric signals, do not show enough genetic diversity to be considered separate species. Furthermore, the data confirm the presence of a yet undescribed species within the genus Campylomormyrus.
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Comparative histology of the adult electric organ among four species of the genus Campylomormyrus (Teleostei: Mormyridae)
Journal of Comparative Physiology A, 2015Co-Authors: Christiane Paul, Jacob Engelmann, Philine G D Feulner, Victor Mamonekene, Ralph Tiedemann, Marianne Vater, Frank KirschbaumAbstract:The electric organ (EO) of weakly electric mormyrids consists of flat, disk-shaped electrocytes with distinct anterior and posterior faces. There are multiple species-characteristic patterns in the geometry of the electrocytes and their innervation. To further correlate electric organ discharge (EOD) with EO anatomy, we examined four species of the mormyrid genus Campylomormyrus possessing clearly distinct EODs. In C. compressirostris , C. numenius , and C. tshokwe , all of which display biphasic EODs, the posterior face of the electrocytes forms evaginations merging to a stalk system receiving the innervation. In C. tamandua that emits a triphasic EOD, the small stalks of the electrocyte penetrate the electrocyte anteriorly before merging on the anterior side to receive the innervation. Additional differences in electrocyte anatomy among the former three species with the same EO geometry could be associated with further characteristics of their EODs. Furthermore, in C. numenius , ontogenetic changes in EO anatomy correlate with profound changes in the EOD. In the juvenile the anterior face of the electrocyte is smooth, whereas in the adult it exhibits pronounced surface foldings. This anatomical difference, together with disparities in the degree of stalk furcation, probably contributes to the about 12 times longer EOD in the adult.
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magic trait electric organ discharge eod dual function of electric signals promotes speciation in african weakly electric fish
Communicative & Integrative Biology, 2009Co-Authors: Philine G D Feulner, Jacob Engelmann, Frank Kirschbaum, Martin Plath, Ralph TiedemannAbstract:A unique evolutionary specialization of African weakly electric fish (Mormyridae) is their ability to produce and perceive electric signals. Mormyrids use their Electric Organs Discharge (EOD) for electrolocation and electrocommunication. Here we discuss the adaptive significance of the EOD in foraging (electric prey detection) in light of recent results demonstrating that mormyrid fish mate assortatively according to EOD waveform characteristics (electric mate choice). Therefore the EOD as a single trait pleiotropically combines natural divergent selection and reproductive isolation. Consequently we postulate the EOD as a “magic trait” promoting the diversification of African weakly electric fish.
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magic trait electric organ discharge eod dual function of electric signals promotes speciation in african weakly electric fish
Communicative & Integrative Biology, 2009Co-Authors: Philine G D Feulner, Jacob Engelmann, Frank Kirschbaum, Martin Plath, Ralph TiedemannAbstract:A unique evolutionary specialization of African weakly electric fish (Mormyridae) is their ability to produce and perceive electric signals. Mormyrids use their Electric Organs Discharge (EOD) for electrolocation and electrocommunication. Here we discuss the adaptive significance of the EOD in foraging (electric prey detection) in light of recent results demonstrating that mormyrid fish mate assortatively according to EOD waveform characteristics (electric mate choice). Therefore the EOD as a single trait pleiotropically combines natural divergent selection and reproductive isolation. Consequently we postulate the EOD as a “magic trait” promoting the diversification of African weakly electric fish.
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adaptive radiation in african weakly electric fish teleostei Mormyridae campylomormyrus a combined molecular and morphological approach
Journal of Evolutionary Biology, 2007Co-Authors: Philine G D Feulner, Victor Mamonekene, Frank Kirschbaum, Valerio Ketmaier, Ralph TiedemannAbstract:We combined multiple molecular markers and geometric morphometrics to revise the current taxonomy and to build a phylogenetic hypothesis for the African weakly electric fish genus Campylomormyrus. Genetic data (2039 bp DNA sequence of mitochondrial cytochrome b and nuclear S7 genes) on 106 specimens support the existence of at least six species occurring in sympatry. We were able to further confirm these species by microsatellite analysis at 16 unlinked nuclear loci and landmark-based morphometrics. We assigned them to nominal taxa by comparisons to type specimens of all Campylomormyrus species recognized so far. Additionally, we showed that the shape of the elongated trunk-like snout is the major source of morphological differentiation among them. This finding suggests that the radiation of this speciose genus might have been driven by adaptation to different food sources.
Peter Rask Møller - One of the best experts on this subject based on the ideXlab platform.
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electric organ discharge displays during social encounter in the weakly electric fish brienomyrus niger l Mormyridae
Ethology, 2010Co-Authors: Peter Rask Møller, J Serrier, Deborah BowlingAbstract:We investigated the electric organ discharge (EOD) activity of the mormyrid fish Brienomyrus niger during social encounters. The fish were contained in porous ceramic shelters and tested alone and in pairs in an experimental tank designed to restrict communication to the electrosensory modality. We moved one fish toward and away from a stationary conspecific, beginning at a distance known to be outside the range of communication (250 cm). Baseline EOD activity was recorded prior to interaction and categorized as ‘variable’, ‘regular’, and ‘scallop’. When moved closer together, the fish modulated this baseline activity in four ways: (1) At 100–130 cm apart, the stationary fish emitted a maximum of sudden EOD rate increases which defined the outer limit of its communication range. (The associated Electric Field Gradient was 1 μV/cm). (2) Long EOD cessations, which we called social silence, lasted from 5–130 s and occurred most frequently when the fish were 36 to 55 cm apart (EFG: 100 μV/cm). The duration of social silence was negatively correlated (r = − 0.862) with the responding fish's size, and was independent of the partner's sex and size. Fish whose EOD baseline pattern was ‘scallop’ were least likely to fall electrically silent, and those that were categorized as ‘regular’ or ‘variable’ were most likely to cease discharging. (3) Within electrolocation range, fish ‘regularized’ their EOD activity while the partner was ‘silent’ (EFG: 1 mV/cm). (4) Following long EOD cessations the fish resumed discharging with characteristic EOD rebound patterns. The possible ethological significance of these findings is discussed.
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The anal fin complex in a weakly discharging electric fish, Gnathonemus petersii(Mormyridae)
Journal of Fish Biology, 2005Co-Authors: L. Greisman, Peter Rask MøllerAbstract:An examination of the permanent bony structures of the anal fin complex in the mormyrid fish, Gnathonemus petersii, revealed two new structural sexual dimorphisms: longer proximal pterygiophores and wider anal fin rays in males than in females. Both structures are thought to facilitate the male’s courtship-associated anal fin reflex. Adult male mormyrid fishes are characterized by a dorsally directed indentation of the posterior body wall (anal fin indentation). The expression of this indentation in males, presumably driven by anal fin musculature, was correlated with the fish’s gonadal state: large indentations were associated with high gonado-somatic indices and small indentations with low indices.
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effects of social interaction on the electric organ discharge in a mormyrid fish gnathonemus petersii Mormyridae teleostei
The Journal of Experimental Biology, 2003Co-Authors: Thomas A Terleph, Peter Rask MøllerAbstract:African weakly discharging electric fish (Mormyridae) use their self-generated electric signals and electroreceptive abilities for orientation and communication in the context of courtship and territorial interactions. This paper documents socially mediated changes in the electric organ discharge (EOD) of subadult Gnathonemus petersii under non-breeding environmental conditions. Increases in EOD duration and changes in the relative phase amplitudes occurred in dominant fish during same-sex (male-male, female-female) and opposite-sex interactions. Similar changes were also observed in fish that were restricted in their physical interactions, suggesting that direct contact is not necessary to induce dominance-typical EOD waveforms. The possible communicative functions of these changes are discussed.
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a sexually dimorphic basal anal fin ray expansion in the weakly discharging electric fish gnathonemus petersii
Journal of Fish Biology, 1998Co-Authors: B. Pezzanite, Peter Rask MøllerAbstract:Male Gnathonemus petersii (Mormyridae) exhibit two structural, sexually dimorphic characters: anal-fin ray bone expansion and an indentation of the posterior ventral body wall (formerly described as anal-fin indentation). Females lack this bone expansion, but may show a slight indentation. Morphometric data on both characters were obtained from radiographs of 414 fish (males and females) ranging in size from 60 to 276 mm Ls. Both body wall indentation and bone expansion began to develop in males of about 120 mm Ls. At 160–180 mm, the sex ratio of fish with expansion to fish without expansion was 50 : 50. Androgens seem to affect the expression of both these sexual dimorphisms. Bone expansion may provide increased bone surface for muscle attachment and thus facilitate the anal-fin reflex during courtship behaviour.
Bernd Kramer - One of the best experts on this subject based on the ideXlab platform.
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a morphological study on species of african mormyrus teleostei Mormyridae and their electric organ discharges
African Journal of Aquatic Science, 2013Co-Authors: Bernd KramerAbstract:Five species of Mormyrus Linne 1758, three from West Africa and one each from East and southern Africa, were compared morphologically, and their electric organ discharges (EODs) recorded in the field. The five species were morphologically well differentiated in terms of principal components analysis and discriminant analysis, with syntopical M. rume Valenciennes 1846 and M. subundulatus Roberts 1989 very close to but distinct from one another. Half the variation in the dataset was captured by PC1 alone, being mainly loaded by caudal peduncle depth and length, anal fin length, length of snout, pre-anal length, and dorsal fin ray count and length, in that order. Allopatric samples of M. lacerda Castelnau 1861 from the Upper Zambezi/Kwando system and Cunene River, Namibia, showed some differentiation regarded as infrasubspecific, similar to that of the M. rume samples from the Bandama River compared to those of the Comoe River, both in Cote d'Ivoire. The EODs, normalised to 25 °C, varied in average duration ...
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novel electrosensory advertising during diurnal resting period in male snoutfish marcusenius altisambesi Mormyridae teleostei
Journal of Ethology, 2011Co-Authors: Peter Machnik, Bernd KramerAbstract:During the day, weakly electric snoutfish, such as Marcusenius altisambesi from the Okavango delta, avoid visually oriented predators by hiding in sheltered, dark places where they discharge their electric organs at a low and variable rate, interspersed with occasional short bursts (mean discharge rate, 4–12 Hz). Hence, histograms of inter-discharge intervals (IDI) are broad and bimodal (IDI range, about 15–500 ms; “variable IDI pattern”). We report here that with a female neighbor in electrical communication reach, captive males of M. altisambesi (N = 4) each showed a novel type of IDI resting pattern that was characterized by a higher and more constant discharge rate (16–28 Hz). These IDI histograms were unimodal and narrow (IDI range, about 11–100 ms; “regularized IDI pattern”). In each of these males, the regularized pattern vanished when the female neighbors were replaced by males, and the common variable IDI pattern of low rate was observed instead. In an unforced choice paradigm, six M. altisambesi experimental females were allowed to choose between two electric fish decoys, one playing back the novel regularized IDI pattern and one playing back the variable IDI pattern. Five experimental females significantly preferred staying close to the decoy playing back the regularized IDI pattern, whereas one female showed the opposite preference. It appears that males advertise to females during their diurnal period of overt inactivity, with an inconspicuous signal that neither threatens conspecifics nor alerts predators by overt behavior. A secondary function of the regularized male IDI pattern could be to advance the reproductive cycle of females.
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trained weakly electric fishes pollimyrus isidori and gnathonemus petersii Mormyridae teleostei discriminate between waveforms of electric pulse discharges
Ethology, 2010Co-Authors: Christian Graff, Bernd KramerAbstract:Fish of the family Mormyridae emit weak, pulse-like electric organ discharges (EODs). The discharge rhythm is variable, but the waveform of the EOD is constant for each fish, with species- and individual characteristics. The ability of Pollimyrus isidori and Gnathonemus petersii (Mormyridae) to discriminate between different EOD waveforms was tested using a differential conditioning procedure. Fish were first trained to respond to a reference signal in swimming to a dish to receive a bloodworm (food reward). The reference signal consisted of a 10-Hz train of the digitally recorded EOD of a conspecific. Second, an alternative signal (10-Hz train of a different EOD, either from another species, or from a conspecific of the other sex) was associated with air bubbles as punishment. The two signals were played at successive trials in random order. On each trial the latency was measured between the onset of the signal and the response. 7 out of the 8 P. isidori tested and both of the two G. petersii tested associated the reference EOD with food. Among these, five P. isidori and two G. petersii responded differentially (p < 0.01) to EODs of different species. P. isidori similarly discriminated between conspecific EODs of different sexes. The quantity of different alternative EODs which could be tested was limited when fish eventually habituated to the punishment. Even when the amplitude of the EODs was randomly changed at each trial, two out of two G. petersii differentiated between EODs of the two species, and three out of three P. isidori tested differentiated between EODs within their own species. Response latencies to the rewarded signal during the basic training and during discrimination (when it had to be distinguished from the S-) were similar. G. petersii showed differential responses for S+ and S- also in the rhythm of discharge exhibited during playback, after five EOD pulses for one fish, and after a single pulse for the other. Mormyrids may therefore distinguish between conspecifics and members of other species, and even between individual conspecifics, by their EOD waveform.
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electrocommunication and social behaviour in marcusenius senegalensis Mormyridae teleostei
Ethology, 2010Co-Authors: Andreas Scheffel, Bernd KramerAbstract:The electric organ discharges (EODs) of Marcnsenius senegalensis, a West African freshwater fish, are bipolar pulses of short duration (220 ± SE 13µs )I.n males (n= 10; 10.1-13.1 cm standard length-which is around the size of getting mature), the duration of EOD pulses was of significantly greater variance than in females (n = 9; 9.8-12.8 cm standard length). Male EODs also showed a tendency for a longer duration than female EODs. Groups of three as well as of 14 M. senegalensis formed temporary schools in a 'naturally' equipped 720-l tank. While swimming slowly in a loose school during their nocturnal active phase, fish discharged in irregular long-short-long inter-EOD interval patterns. Near neighbours displayed a tendency to discharge in intervals of similar duration (nearest neighbour distance < 1/2 fish length). On removal of a plastic partition that had separated a pair of fish for at least 3 days, mutual threat displays followed by fighting were observed. During threatening, the fish alternated regularly between bursts of a high discharge rate and short discharge breaks; the rate of change was 4/s. The subdominant animal in a group of two was attacked frequently and often ceased discharging when the dominant fish approached. Courtship behaviour involving gonadally mature fish was accompanied by highdischarge- rate displays with intervals of constant duration in both fish, and the reciprocal display of 'preferred' EOD latencies in the 12 ms range. The results demonstrate electric communication by distinct inter-discharge interval patterns in the social behaviour of this mormyrid fish.
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differentiation of courtship songs in parapatric sibling species of dwarf stonebashers from southern africa Mormyridae teleostei
Behaviour, 2006Co-Authors: Michael Lamml, Bernd KramerAbstract:We describe the nocturnal courtship songs of male dwarf stonebashers, Pollimyrus castelnaui, from the Okavango River and its inland delta. We examined the question of whether the songs are sufficiently differentiated from those of its parapatric sibling species, the only recently discovered P. marianne from the Upper Zambezi River, to form a potential cue for mate choice. Both species vocalised two sound types in courtship, the moan and the grunt, which they combined into long songs in similar fashion. However, one sound type was clearly differentiated: while P. castelnaui moans were of a husky quality and composed of three or four broadband formants, P. marianne moans were more tonal, with a single spectral line dominating the first and any higher formants (and a smaller bandwidth BW−10 dB for the dominant frequency of the first formant). Moan and Grunt Duration and the moan Pulse Group Period (mPGP) were longer, and the latter more variable, in P. castelnaui compared to P. marianne (range of mPGP: 10-30 ms in P. castelnaui, 7-16.7 ms in P. marianne). P. castelnaui grunts were of longer duration and composed of more pulses than those of P. marianne. A single male from the contact zone between the Okavango and the Zambezi, the lower Kwando River, resembled P. castelnaui in moan BW−10 dB but P. marianne in Moan Duration and mPGP. Both southern African species thus vocalise in a species-specific fashion. Since in both species several characteristics of both moans and grunts show high between- and low within-male variability, mate choice may be selective for individual high-quality males characterised by acoustic features.
